Polarographic determination of neptunium without uranium separation

Technique of neptiunium determination, comprising electrochemical cycle of solution preparation, which consists of uranium reduction to Usup((4)), plutonium to Pusup((3)), neptunium to Npsup((3)) at E=-0.6 V/NHE with subsequent selective oxidation of neptunium to Npsup((4)) at E=+0.05-0.1 V/NHEh, is presented. Polarographic analysis is carried out according to the transition Npsup((4)) → Npsup((3)) - on mercury dropping electrode (MDE) in alternating-current regime. To increase the technique selectivity at the mass ratio U/Np >= 5x103.concentration of sulphuric acid in the background electrolyte is increased to 3 mol/l. When analyzing model solutions of approximate composition U-1 mol/l, HNO3 - 2 mol/l, Np - 2x10-4 mol/l it is shown, that total error of the technique is lower (Δ approximately equal to 2-3%) when the method of additions is used, than that of calibration diagram. For the concrete variant of the technique the calculation formula of the method of additions is transformed